sctp: fix some rhashtable functions using in sctp proc/diag

When rhashtable_walk_init return err, no release function should be
called, and when rhashtable_walk_start return err, we should only invoke
rhashtable_walk_exit to release the source.

But now when sctp_transport_walk_start return err, we just call
rhashtable_walk_stop/exit, and never care about if rhashtable_walk_init
or start return err, which is so bad.

We will fix it by calling rhashtable_walk_exit if rhashtable_walk_start
return err in sctp_transport_walk_start, and if sctp_transport_walk_start
return err, we do not need to call sctp_transport_walk_stop any more.

For sctp proc, we will use 'iter->start_fail' to decide if we will call
rhashtable_walk_stop/exit.
Signed-off-by: NXin Long <lucien.xin@gmail.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

net/sctp/proc.c

@@ -280,6 +280,7 @@ void sctp_eps_proc_exit(struct net *net)
 struct sctp_ht_iter {
 	struct seq_net_private p;
 	struct rhashtable_iter hti;
+	int start_fail;
 };
 
 static void *sctp_transport_seq_start(struct seq_file *seq, loff_t *pos)
@@ -287,8 +288,10 @@ static void *sctp_transport_seq_start(struct seq_file *seq, loff_t *pos)
 	struct sctp_ht_iter *iter = seq->private;
 	int err = sctp_transport_walk_start(&iter->hti);
 
-	if (err)
+	if (err) {
+		iter->start_fail = 1;
 		return ERR_PTR(err);
+	}
 
 	return sctp_transport_get_idx(seq_file_net(seq), &iter->hti, *pos);
 }
@@ -297,6 +300,8 @@ static void sctp_transport_seq_stop(struct seq_file *seq, void *v)
 {
 	struct sctp_ht_iter *iter = seq->private;
 
+	if (iter->start_fail)
+		return;
 	sctp_transport_walk_stop(&iter->hti);
 }
 

net/sctp/socket.c

@@ -4299,8 +4299,12 @@ int sctp_transport_walk_start(struct rhashtable_iter *iter)
 		return err;
 
 	err = rhashtable_walk_start(iter);
+	if (err && err != -EAGAIN) {
+		rhashtable_walk_exit(iter);
+		return err;
+	}
 
-	return err == -EAGAIN ? 0 : err;
+	return 0;
 }
 
 void sctp_transport_walk_stop(struct rhashtable_iter *iter)
@@ -4389,11 +4393,12 @@ EXPORT_SYMBOL_GPL(sctp_transport_lookup_process);
 int sctp_for_each_transport(int (*cb)(struct sctp_transport *, void *),
 			    struct net *net, int pos, void *p) {
 	struct rhashtable_iter hti;
-	int err = 0;
 	void *obj;
+	int err;
 
-	if (sctp_transport_walk_start(&hti))
-		goto out;
+	err = sctp_transport_walk_start(&hti);
+	if (err)
+		return err;
 
 	sctp_transport_get_idx(net, &hti, pos);
 	obj = sctp_transport_get_next(net, &hti);
@@ -4407,8 +4412,8 @@ int sctp_for_each_transport(int (*cb)(struct sctp_transport *, void *),
 		if (err)
 			break;
 	}
-out:
 	sctp_transport_walk_stop(&hti);
+
 	return err;
 }
 EXPORT_SYMBOL_GPL(sctp_for_each_transport);